Terraforming Wiki

Greenhouse effect

There are a few ways an Inner Planet can be cooled and made habitable. All methods are more expensive then what is needed to heat an Outer Planet. The known methods include: anti-greenhouse gasses, anti-greenhouse fogs, artificial objects (in the atmosphere or the outer space) and others.

Anti Greenhouse Gasses[]

Main article: Anti Greenhouse Gasses.

These gasses reflect part of the light and heat. Left alone, they have a greenhouse effect. However, if they are extremely short lived (with a half-life of a day), they can cover specified areas during day, while in night, they vanish, allowing heat to escape into space. Other gasses have a half-life around an year. They can be deployed around the equator, to reflect solar radiation, preventing certain areas from warming. Since they will need time to reach the poles, there, heat will escape into space.

These methods might be useful for a planet orbiting between Earth and Venus, but certainly will not be useful closer to the Sun then Venus.

Anti Greenhouse Particles[]

The technology is similar, but instead of gasses, we will use water droplets or small particles. There are a few ways to do this:

  1. Artificial clouds. There are chemicals able to help atmospheric water to condense. The cheapest and most easy to find is salt. By deploying tiny crystals of salt in the upper atmosphere, they will absorb moisture and create a cloud. If there is not enough moisture, we could also spray droplets of water. These clouds could reflect part of solar light, keeping temperature low for a while.
  2. Cloud cleansing. There are other chemicals able to dissolve clouds. This technology can be used during night, to allow heat from the atmosphere radiate into the outer space.
  3. Atmospheric powders. It is possible to dump in the upper atmosphere small particles, that will reflect a percent of solar radiation.

All these solutions are for the moment. Cooling an area with clouds and powders will require a permanent fleet of airplanes or stratospheric rockets, which would automatically imply huge maintenance costs. There are many side effects: chemicals might be toxic (for example salt would result in salt rains, while other substances would create acid or toxic rains). Powders will slowly move down to the surface, where they will cover all buildings and vegetation with a thick white layer, just as one can see around some cement factories.

These methods might be useful for a planet orbiting between Earth and Venus, but certainly will not be useful closer to the Sun then Venus.

Anti Greenhouse Flying Objects[]

There are a few methods that can cool a planet with the help of manmade objects:

  1. Cosmic mirrors and lens can deflect part of solar light. Some people suggest the use of large mirrors (over 1 km), while others argue that the mirrors and lens should be smaller then 1 cm.
  2. Atmospheric mirrors can be made under the form of balloons, flowing at a specified height and coated with a reflective material.
  3. Micro Helium Balloons. This technology requires the use of very small balloons (smaller then 1 cm), flying at a specified height.

The use of cosmic mirrors and lens could be a solution for any inner planet. The method might be very expensive in case of a planet closer to the Sun then Mercury, which would require over 90% of light to be reflected. In that case, mirrors will need to be placed in many layers, on different and complex orbits. The major problem is that having too many objects flying on close orbits is risky. Collisions will damage the mirrors and the lens. In time, they will tend to move closer and form a ring, reducing the protective effect. Spaceships passing through the area will be at risk.

The second method could also be used for cooling inner planets. The problem is that balloons are usually fragile and will break apart in collisions and during lightning. They will also endanger airplanes and spaceships. On a planet closer to the Sun then Venus, where over 60% of the light needs to be reflected, we will need enough balloons to cover over 60% of the sky, which will not be feasible.

The third method, even if expensive, could be the only solution for hot inner planets. For more details, see Micro Helium Balloons.

Other methods[]

Other methods include painting large areas in white or whitening the oceans by creating microbubbles. Both are expensive and might be useful for a planet orbiting between Earth and Venus.

In the far future, it might be possible to create a planetary shield, able to allow only certain amounts of radiation to reach the planet.